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Chemie der Erde 74 (2014) 393–406

Contents lists available at ScienceDirect

Chemie der Erde

j o ur na l ho mepage: www.elsev ier .de /chemer

ineralogy and speciation of Zn and As in Fe-oxide-clay aggregates inhe mining waste at the MVT Zn–Pb deposits near Olkusz, Poland

rena Jerzykowskaa, Juraj Majzlanb,∗, Marek Michalika, Jörg Göttlicherc,alph Steiningerc, Artur Błachowskid, Krzysztof Ruebenbauerd

Institute of Geological Sciences, Jagiellonian University, Oleandry 2a, 30-063 Krakow, Poland1

Institute of Geosciences, Friedrich-Schiller University, Burgweg 11, D-07749 Jena, GermanyKarlsruhe Institute of Technology, ANKA Synchrotron Radiation Facility, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, GermanyMössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorazych 2, PL-30-084 Kraków, Poland

r t i c l e i n f o

rticle history:eceived 11 December 2013ccepted 23 March 2014ditorial handling - F. Langenhorst

eywords:ining wasteineralogy

nvironmental pollutionlemental speciation

a b s t r a c t

Oxidation zones of ore deposits offer valuable insights into the long-term fate of many metals and met-alloids. In this work, we have studied a paleo-acid rock drainage (ARD) system – the oxidation zoneof Mississippi-valley type Zn–Pb deposits near Olkusz in southern Poland. The ARD systems exhaustedtheir acid-generating capacity and have come almost to the conclusion of the mineral and geochemicaltransformations. Primary pyrite, marcasite, galena and sphalerite have been decomposed but the aciditywas neutralized by the abundant carbonate host rocks. Zinc is stored in smithsonite, hemimorphite, andZn-rich sheet aluminosilicates. Some of these minerals formed simultaneously with the oxidation zonebut some precipitated in the soils in situ, thus documenting the mobility of Zn, Al, and Si in the soils. Ironoxides are represented mostly by goethite, either well-crystalline or nanocrystalline, as determined bya combination of powder X-ray diffraction, micro-X-ray diffraction, and Mössbauer spectroscopy. Ironoxides bind a substantial amount of arsenic, to a lesser extent also zinc, lead, and cadmium, as shownby electron microprobe analyses and sequential extractions. The X-ray absorption spectroscopy data ofthe local environment of arsenic in goethite suggest the existence of bidentate mononuclear complex, inaddition to the more common bidentate binuclear complex. These results suggest that arsenic is incor-porated in the crystal structure of goethite, in addition to adsorbed to the surface of the particles oroccluded in the voids and pores. Zinc is bound in goethite as a mixture of tetrahedrally and octahedrallycoordinated cations. This study shows that the mature system binds the metals from the primary sulfidesrelatively strongly. Yet, some release of the metals was observed in this study, either in the laboratory

(by sequential extractions) and in nature (e.g., neoformed Zn phyllosilicates). The physical conditionsin the oxidation zone and on the surface are largely similar but the metals, to a certain extent, are stillmobile in the soils. We may speculate that their mobility near the surface, in the mining waste, may beenhanced by a higher water/rock ratio than in the oxidation zone. This result implies that although thestudied material is relatively benign, it still has a potential to cause local environmental problems.

© 2014 Elsevier GmbH. All rights reserved.

. Introduction

Oxidation zones of ore deposits offer valuable insights into the

ong-term fate of many metals and metalloids. They are a windowhrough which we can peek into the future and examine the fatef metal-rich waste forms over long-term periods. Mineralogy of

∗ Corresponding author. Tel.: +49 3641 948700; fax: +49 3641 948702.E-mail address: juraj.majzlan@uni-jena.de (J. Majzlan).

1 Current address: Institute of Geological Sciences, Polish Academy of Sciences,esearch Centre in Cracow, Senacka 1, 31-002 Kraków, Poland.

ttp://dx.doi.org/10.1016/j.chemer.2014.03.003009-2819/© 2014 Elsevier GmbH. All rights reserved.

the oxidation zones provides abundant evidence of many sinks ofmetals and metalloids; for example, the well-developed oxidationzone in Tsumeb has yielded so far more than 250 minerals, manyof them secondary (Lombaard et al., 1986). In comparison to thesuperb example of Tsumeb, other oxidation zones appear less richand interesting but they are, in their own right, an exciting source ofinformation about mineral transformations and element migrationpatterns.

In this contribution, we have examined the mine waste fromthe oxidation zone of Mississippi-valley type (MVT) Zn–Pb depositsnear Olkusz in southern Poland (Sass-Gustkiewicz and Dzułynski,1998; Cabała, 2001). The objectives of the present study were to

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i) identify the secondary minerals, (ii) evaluate the leachability ofetals and metalloids from them, and (iii) determine speciation

f As and Zn, two major pollutants, in these minerals. We havesed a combination of bulk (XRF analysis, sequential extraction)nd micro-methods (electron microprobe, X-ray microdiffraction,-ray absorption microspectroscopy) to achieve these goals.

. Geological settings and history of the deposit

Sulfide MVT deposits in the Cracow–Silesia region are hostedy the Triassic carbonate rocks of the Cracow–Silesian Mono-line (Buła and Zaba, 2008). Beneath the Permo-Mesozoic rocks,he Cracow–Lubliniec fault zone divides Precambrian to Paleo-oic tectonic units – Upper Silesian Block (Brunovistulicum) andałopolska Blok. Host rocks of the ores are the so-called ore-

earing dolomites (OBD) that occur down to 300 m below theround level as tabular bodies in the sequence of middle Trias-ic carbonate rocks (Bogacz et al., 1975; Sass-Gustkiewicz andzułynski, 1998). Several stages of hydrothermal sulfide mineral-

zation resulted in the formation of a few generations of sulfides.he dominant minerals are sphalerite (ZnS), marcasite (FeS2),yrite (FeS2), and galena (PbS) (Haranczyk, 1962; Sass-Gustkiewicznd Kucha, 2005), As and Pb sulfosalts are less common (Kucha andiaene, 1993).

From late Cretaceous to middle Miocene, with most favor-ble weathering conditions from early Paleogene to middleiocene (Coppola et al., 2009; Strzelska-Smakowska, 2010), an

xidation zone has developed in the tectonic horsts and placesithout clay cover over sulfide deposits. Supergene non-sulfideeposits form tabular bodies, nests, and lenses in OBD (Zabinski,960). Most of the non-sulfide deposits were exploited untilhe mid-1980s. The remaining ∼57 million tons of ores con-ain around 5.6 wt.% Zn and 1.4 wt.% Pb (Coppola et al., 2009).

ain components of the non-sulfide deposits are Zn carbo-ates (mainly smithsonite, ZnCO3), goethite (FeOOH), remnantsf sulfides and cerussite (PbCO3) (Zabinski, 1960). HemimorphiteZn4[Si2O7(OH)2]·H2O}, jarosite [KFe3(SO4)2(OH)6], melanteriteFeSO4·7H2O), epsomite (MgSO4·7H2O), gypsum (CaSO4·2H2O),ydrozincite [Zn5(CO3)2(OH)6], anglesite (PbSO4), psilomelanea mixture of Mn oxides), pyrolusite (MnO2), Zn-dolomiteCa(Mg,Zn)(CO3)2], greenockite (CdS) (Zabinski, 1960; Gałkiewicz,983; Cabała, 2009) and Zn-smectites (Zn–Al sheet silicates, seeelow) (Coppola et al., 2009) occur rarely.

Mining activity in the region Olkusz was carried out with briefnterruptions from the Middle Ages to the present day (Cabała,009). It resulted in a significant transformation and pollution ofarious components of the environment, including water and riverediments (Helios-Rybicka, 1996a,b; Ciszewski and Malik, 2003,004; Van Roy et al., 2006; Aleksander-Kwaterczak and Helios-ybicka, 2008; Aleksander-Kwaterczak et al., 2010; Ciszewski,010) and soil (Chłopecka, 1996; Chłopecka et al., 1996; Trafas,996; Verner et al., 1996; Mayer et al., 2001; Krzaklewski et al.,004; Cabała et al., 2004, 2008, 2009; Gruszecka and Helios Rybicka,006; Cabala and Teper, 2007; Chrastny et al., 2011). The mainources of soil pollution are smelter emissions and the old miningumps (e.g., Chrastny et al., 2011).

. Materials and methods

Samples were collected at three sites (14, 17, 24, and 25) where supergene non-ulfide mining wastes from four open pits ‘Bolesław’ (site 14), ‘Krazek’ (sites 24 and5), ‘Ujków Stary’ (site 17) were deposited between the end of 19th century and985 (Cabała, 2009). Dump site 14 is the oldest among the studied ones. Sites 14

nd 17 are covered by spontaneously overgrown thermophilous grassland calledalamine grassland and the sites 24 and 25 by afforested Scots pine (Kapusta et al.,011; Grodzinska et al., 2010). Investigated soils are shallow (20–30 cm) and skele-al Technosols (FAO World Reference Base for Soil Resources) resembling initialendzinas (Lis and Pasieczna, 1999; Kapusta et al., 2011) with poorly developed soil

Fig. 1. Photograph of the profile 14b with indication of the individual sampledhorizons.

profiles. At each site, around 2 kg samples were collected from two soil profiles (aand b), each profile comprising 3 or 4 horizons (Fig. 1), distinguishable from eachother by color. From the lowermost horizons, dump rocks samples were taken. Col-lected samples were stored in open plastic bags in dry air conditions. For furtherinvestigation, selected samples were prepared in a form of thin sections, suitablefor the methods with microscopic resolution.

Soil samples were sieved to a fraction <1 mm and then mixed in ratio 1:2.5 withdeionized water or 1 M KCl solution. pH of soil-solution mixture was measured after24 h, using a pH electrode Elmetron CP–401. For bulk chemical composition, sam-ples were ground in �-WC ball mill and analyzed using inductively coupled plasmaatomic emission spectrometry (ICP AES) and inductively coupled plasma mass spec-trometry (ICP MS) methods (at the Acme Analytical Laboratories, Canada). Sampleswere fused with lithium metaborate (LiBO2) and lithium tetraborate (Li2B4O7) anddissolved in HNO3 for ICP AES analyses of the main components and ICP MS analysesof Zn, Pb, As, Cd and trace elements. The content of Zn, Pb, As and Cd was measuredagain using ICP AES for which samples were heated and mineralized in acids: HF,HClO4, HNO3 and distilled water in the ratio 2:2:1:1.

Seven-step sequential extraction was carried out in duplicate for 0.5 g of each ofthe soil samples (<1 mm) and dump material (ground in an agate-mortar), accord-ing to modified procedure of Kersten and Forstner (1986) and Tessier et al. (1979).The sample/solution ratio, solution molarities, time and conditions of treatment aresummarized in Table 1.

Samples were weighed before each step, centrifuged after reaction(>10,000 rpm, 10 min), and weighed with the remaining solution after decantingthe supernatant. Extracts after each step were filtered, acidified with a few dropsof HNO3, stored in 4 ◦C and sent for elemental analyses immediately after thecompletion of the whole experiment. Control samples with Merck ICP standards(traceable to NIST-SRM CertiPUR®) were examined simultaneously with eachanalysis. The amount of trace elements in chemical reagents was also checked.

Concentration of Zn, Pb, As and Cd in extracts was examined using ICP AES instru-ment Perkin Elmer Thermo Scientific method in the laboratory of the VoivodshipInspectorate for Environmental Protection in Cracow. After the chemical analysis,correction for Zn, Pb, As and Cd in the solution remaining after each step was countedbasing on sample weight, weight of the remaining solution, and reagent density.Average recovery, which represents sum of each element from all the steps ofsequential extraction and the bulk chemical analysis, is 87% which is in a good agree-ment with previous studies (e.g., Anju and Banerjee, 2010). Sequential extractionmethod compared with detailed mineralogical analyses is a suitable tool to quan-

titatively determine the forms of elements occurrence in polluted soils. Observeddiscrepancies in the results can be improved by examining the residue after eachstep of extraction (Kierczak et al., 2008).

Mineral composition of samples was determined using optical microscopy (pol-ished thin sections), SEM-EDS analysis (HITACHI S-4700 field emission microscope

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Erde 74 (2014) 393–406 395

fitted with energy dispersive spectrometer), and a powder X-ray diffraction (PHILIPSX’Pert APD) in the Institute of Geological Sciences, Jagiellonian University, Poland.SEM-EDS analyses were performed with analytical spot ca. 1 �m, accelerating volt-age 20 kV, beam current 10 nA, and counting time 60 s. During XRD analyses, thesamples were irradiated by Cu K� radiation at room temperature and the data werecollected in the range of 2–64◦2�, with a step of 0.02◦2� and dwell time of 1 s. Clayfraction was separated according to Jackson (1974) and Mehra and Jackson (1960).Samples were saturated with Na and Mg. Oriented specimens were analyzed in dryair conditions, after glycol saturation and after heating to 330 ◦C and 550 ◦C.

Samples from sites 17a and 24a were also studied with electron microprobe(EMP) Jeol JXA-8530F HyperProbe in Centre for Experimental Mineralogy, Petrologyand Geochemistry (CEMPEG), University of Uppsala. The analyses were carried outin wavelength-dispersive (WDS) mode. Fourteen elements: As (with the standardGaAs), Pb (Pb5(VO4)3Cl) Zn, S (ZnS), Cd (Cd), Fe (Fe2O3), Ca, Si (CaSiO3), Mn, Ti(MnTiO3), Ba (BaSO4), Mg (MgO), Al (Al2O3), K (KAlSi3O8) were analyzed in the(WDS) mode with analytical spot 1–5 �m, accelerating voltage 15 kV and beam cur-rent 5–10 nA. All elements were measured on K� lines except of As (L�), Cd (L�)and Pb (M�). Counting times were 10 s except from As (50 s) and Fe (20 s).

For the electron microprobe (EMP) analyses with the JEOL JXA-8230 instru-ment at the University in Jena, Germany, the thin sections were analyzed in thewavelength-dispersive mode for As (with the standard InAs), Mg (MgO), Al (Al2O3),Si and Ca (wollastonite), Ti (rutile), Pb (PbS), K (orthoclase), S (pyrite), Zn (Zn metal),Mn (Mn metal), and Fe (hematite). The analytical conditions were 15 kV, 5 nA, beamdiameter 1–5 �m. Time at the peak was 10 s and at the background 5 s. The back-scattered electron (BSE) images were also acquired with this instrument.

Aggregates of Fe oxides from the samples 17a and 24a were selected using abinocular and subjected to a Mössbauer spectrometry analysis. About 100 mg ofthe aggregates were ground in an agate mill and mixed with B4C. Mössbauer spec-tra were obtained at room temperature (RT) for all selected samples and for 24aand 24b also at 80 K using conventional Mössbauer spectrometer RENON MsAa-3in transmission mode. Low temperature was maintained by the Janis SVT-400Mcryostat. Fits to the data were performed using the software package Mosgraf-2009(Ruebenbauer and Duraj, 2009).

The micro-X-ray diffraction (�-XRD) and micro-X-ray absorption spectroscopy(�-XAS) data were collected at the beamline of the Synchrotron Radiation Labo-ratory for Environmental Studies (SUL-X, Angströmquelle Karlsruhe, Germany) inthe synchrotron radiation source ANKA. For this work, the samples polished to athin section were detached from the supporting glass resulting in self-supportingfoils which maintained the grains of secondary minerals in a position for the mea-surement without the interference of X-ray scattering of the supporting material.A silicon (1 1 1) crystal pair with a fixed beam exit was used as a monochromator.The X-ray beam was aligned to an intermediate focus, and then collimated by slitslocated at the distance of the intermediate focus to about 100 �m × 100 �m andsubsequently focused with a Kirkpatrick-Baez mirror pair to about 50 �m × 50 �mat the sample position.

The �-XRD data were acquired in transmission mode with a CCD detector (Pho-tonic Science XDI VHR-2 150). For our experiments, the beamline was operated at14 keV (� = 0.886 A). Powdered Si (NIST 640d) was used to calibrate the diffractionangles. The images were integrated with the program Fit2D (Hammersley et al.,1996) and the 1D XRD patterns were further used for Rietveld refinement with theprogram GSAS (Larson and von Dreele, 1994) after background subtraction.

The �-XAS spectra at As K edge and Zn K edge were measured in fluorescencemode in energy steps of 5 eV in the region from −150 to −50 eV relative to theabsorption edge, of 2 eV in the region from −50 eV to −20 eV, of 0.4 eV from −20 eVto +20 eV, and with a k step of 0.05 from +20 eV to +850 eV (about k = 15, usableup to about k = 13 for As, and up to about k = 12 for Zn). Energy has been calibratedto 11.919 eV (maximum of first derivative) with a Au foil for the As K-edge andto 9659 eV (maximum of the first derivative) with a Zn foil for the Zn K edge. Theintensity of the primary beam was measured by an ionization chamber. Fluores-cence intensities were collected with a 7 element Si(Li) solid state detector (SGXSensortech, formerly Gresham) with the energy window set to the As K� or Zn K�fluorescence emission line. Data were dead time-corrected, summed up for all sevenchannels and divided by the input intensity, which was measured in an ionizationchamber prior to the sample analysis. The collected data were processed by Athenaand Artemis software suite (Ravel and Newville, 2005).

4. Results and discussion

4.1. General description and chemical composition of the studiedmaterial

The examined soils are skeletal, characterized by sandy-loamtexture (USDA Soil Texture) and pH close to neutral (pHH2O 6.8–8.3;Table 2). The uppermost horizons contain numerous fragments

of organic matter in different stages of decomposition and smallspherical particles deposited from atmospheric pollution fromsmelters or power plants (Cabala and Teper, 2007; Cabała et al.,2009) and quartz grains. The results of bulk chemical analyses are

396 I. Jerzykowska et al. / Chemie der Erde 74 (2014) 393–406

Table 2Results of mineralogical and chemical analyses of the samples from the profiles 14 and 17. The semiquantitative mineralogical results show the abundance of each mineral,from absent (–) through rare (•), common (••, •••) to frequent (��, ���) and dominant (����). All chemical data in weight % with the exception of As and Cd (in ppm).LOI = loss on ignition.

14aI 14aII 14aIII 14bI 14bII 14bIII 14bIV 17aI 17aII 17aIII 17bI 17bII 17bIIIpH (H2O) 7.89 7.42 7.83 7.91 7.89 7.87 7.34 7.77 7.42dolomite ●●● ● ●●● ● ●● ● ●●● ● ●●● ● ●● ● ●● ● ●●● ● ●● ● ●● ●●● ● ●● ●●quartz • ●●● ●●● • ●●● ••• ●● • ●●●● ●●●● • ●●●● ●●●●smithsonite •• ••• •• •• ••• ••• ●● - - - - - -hemimorphite - - - - - - - • •• •• • •• ••clays - •• •• - •• •• •• - •• •• - •• •goethite •• •• •• •• •• •• •• - •• •• - •• ••Mn oxides • - • • - - • - - • - - •calcite - - - - - • - • - - •• - -marcasite • - • • - - • - - •• - - ••spha lerite • - •• - •• - • - - •• - - ••galena •• - - - - - - - - • - - -SiO2 1.37 22.07 26.32 2.66 21.39 12.31 17.37 1.35 43.90 37.35 1.52 43.13 48.75TiO2 0.01 0.14 0.25 0.01 0.14 0.08 0.13 0.01 0.16 0.19 0.01 0.14 0.15Fe2O3 6.73 9.66 8.47 21.28 9.98 14.27 12. 01 1.77 9.10 8.72 1.51 10. 52 8.35Al2O3 0.25 3.05 5.63 0.26 2.78 1.82 2.53 0.22 3.15 3.99 0.25 2.93 3.22CaO 26.58 14.74 11.63 21.72 15.28 15.98 13. 17 31. 34 9.83 9.08 31. 80 9.29 8.01MgO 17.17 10.05 7.77 14.24 10.02 10.27 8.56 18. 33 6.36 5.55 18. 00 6.01 5.13ZnO 3.02 7.98 5.46 2.18 6.73 10.28 11.69 0.49 5.46 5.34 0.51 6.16 5.49MnO 0.13 0.47 0.29 0.12 0.32 0.53 0.31 0.25 0.43 0.33 0.21 0.48 0.35PbO 0.44 0.48 0.42 0.26 0.50 0.82 0.57 0.07 0.23 0.51 0.04 0.27 0.35Na2O 0.04 0.06 0.11 0.01 0.06 0.04 0.06 0.05 0.07 0.09 0.07 0.08 0.10K2O 0.04 0.61 0.81 0.04 0.52 0.30 0.38 0.03 0.49 0.54 0.03 0.47 0.52P2O5 0.01 0.05 0.11 0.01 0.07 0.04 0.08 0.01 0.07 0.13 0.01 0.07 0.10LOI 43.70 30.40 32.50 36.60 32.10 33.30 33. 60 45. 60 20. 70 27. 80 45. 60 20. 50 19. 50Total 99.49 99.76 99.77 99.39 99.90 100.04 100 .46 99. 52 99. 96 99. 62 99. 56 100 .05 100 .02As ( ppm) 119.9 345.5 299.2 260.6 414.9 573.6 605 .8 41.7 311 .5 358 .8 44.1 414 .9 333 .0Cd (pp m) 164.8 257.4 187.9 62.3 211.7 364.2 328 .7 122 .5 133 .9 180 .9 96.0 278 .5 155 .4

24aI 24aII 24aIII 24bI 24bII 24bIII 25aI 25aII 25aIII 25bI 25bII 25bIIIpH (H2O) 7.70 7.16 7.69 7.13 7.70 6.82 7.71 7.31dolomite ●●● ● ●● ● •• • ●●● ● •• • •• • ●●● ● ●● ● •• ●●● ● ●●● ● ••quartz • ●●● ● ●●● ● • ●●● ● ●●● ● • ●●● ● ●●● ● •• ●●● ● ●●● ●smithsonite •• •• •• •• •• •• •• •• • •• ●● ● •• • ••hemimor phite • - - - - - - - - - - -clays • • • • • • - - - - - -goethite •• •• •• •• •• •• •• •• •• •• •• ••Mn oxides • - • • - • • - • • - •calcite •• •• • •• - - - •• - •• • •• • -marc asite • - • • - • • - • • - •spha lerite • - • • - - - • - - •• ••galena - - - - - - - - - - - -SiO2 2.90 29.33 30.30 0.98 42.92 37.71 1.99 41. 17 85. 19 2.30 28. 27 86. 14TiO2 0.03 0.26 0.36 <0.01 0.28 0.35 0.02 0.16 0.10 0.01 0.13 0.08Fe2O3 3.66 13.56 10.64 2.66 16.26 14.14 2.08 6.56 1.01 2.02 7.36 1.31Al2O3 0.57 4.44 7.18 0.18 4.66 6.55 0.31 2.96 1.70 0.27 2.85 1.37CaO 28.19 10.46 6.41 28.19 5.57 4.75 29. 41 11. 74 0.72 27. 01 15. 08 1.60MgO 16.21 6.86 3.97 20.00 3.86 2.97 19. 33 7.54 0.30 14. 18 9.78 0.90ZnO 3.93 7.43 4.95 1.85 6.22 5.68 0.86 5.59 0.37 13. 51 7.39 0.91MnO 0.24 0.25 0.23 0.13 0.24 0.23 0.18 0.27 0.03 0.16 0.32 0.04PbO 0.16 0.65 0.56 0.05 0.48 0.53 0.08 0.34 0.0 6 0.09 0.44 0.10Na2O 0.03 0.09 0.17 0.04 0.13 0.18 0.03 0.10 0.10 0.02 0.08 0.07K2O 0.10 0.68 0.89 0.03 0.81 0.89 0.05 0.54 0.38 0.04 0.46 0.33P2O5 0.02 0.10 0.18 0.01 0.08 0.12 <0.01 <0.01 0.01 <0.01 <0.01 <0.01LOI 43.60 26.10 34.00 45.50 19.20 26.50 45. 20 23. 70 10. 10 42. 00 28. 50 7.20Total 99.64 100.21 99.84 99.63 100.71 100.59 99. 53 100 .67 100 .08 101 .60 100 .67 100 .05

33.017.4

lsciesuTea

As ( ppm) 170.1 925.8 573.6 90.4 979.0 831.2 71.6 328 .5 Cd (pp m) 210.5 155.3 172.0 100.2 169.3 182.9 52.7 147 .9

isted in Table 2. The amount of SiO2 varies between 1 wt% in someamples from dump material to 85 wt% in the sample 25aIII whichontains large amounts of quartz grains. High proportion of SiO2n uppermost horizons in comparison to the dump material is thevidence of aeolian origin of quartz (windblown from fluvioglacialands mined nearby). The Al2O3 content is low from about 0.1 wt%p to 6.5 wt% and generally increases to the top of the soil profiles.

he content of Fe2O3 varies between 1 wt% and 21 wt% and is gen-rally higher in soil horizons II than I and III and is associated with

higher content of Fe-oxides.

86.6 383.5 55.6424 .1 215 .4 35.1

The minor and trace elements Zn, Pb, As, and Cd correlate wellwith Fe2O3 (Fig. 2) and hence, just as Fe2O3, they are particularlyenriched in the soil horizon II. The amount of Zn varies from 3 wt% inthe quartz-rich sample 25aIII, 4 wt% in samples from dump materialon the site 17 up to 11 wt% Zn in the smithsonite-rich sample 25bI.Pb amount reaches 6 wt% in sample 24aII, the lowest Pb content of334 ppm was found in sample 17bI. Arsenic varies between 33 ppm

(25aIII) and 979 ppm (24bII), cadmium from 17 ppm (25aIII) to424 ppm (25bI). In most cases, studied elements are enriched inthe soil horizons III and II in comparison to the horizon I (i.e., dump

I. Jerzykowska et al. / Chemie der

F

mt

4

sZ(sw

Fas

ig. 2. A schematic map of the studied area with the positions of the sampling points.

aterial, Table 2). Therefore, the analytical work concentrated onhe horizons II and III.

.2. Mineral composition

Mineral composition of the material from the dumps and soilamples generally resembles the composition of the non-sulfide

n–Pb deposits in this region. Using XRD analyses, carbonatesdolomite, smithsonite, calcite), silicates (quartz, hemimorphite,heet silicates), goethite and sulfides (marcasite, sphalerite, galena)ere identified; Mn oxides were detected only by SEM-EDS and

ig. 3. Scanning electron microphotographs of (a) an association of smithsonite, dolomitn aggregate of smithsonite crystals with etch pits and crusts of Mn oxides; (c) a crystaheet silicates as filling of cavities in an aggregate of hematite crystals.

Erde 74 (2014) 393–406 397

EPM analyses. Semiquantitative abundance of minerals is listed inTable 2. The most common minerals in all samples are dolomite andquartz. There is a distinct difference in mineralogical Zn speciationbetween the profiles 14, 24, 25 and 17: the first three contain abun-dant smithsonite and no hemimorphite. Profile 17, on the otherhand, contains scarce hemimorphite and no smithsonite. Sheet sil-icates were identified in the profiles 14, 17, and 24 but are missing inthe profile 25. Sulfides occur in trace amounts, and when detected,probably represent relics of the primary mineralization. Goethitewas detected in all but two (17aI and 17bI) samples.

The semiquantitave mineral composition (Table 2) correlateswell with the bulk chemical composition (Table 2). Principal-component analysis (PCA) of the bulk-chemical data identifiedthree principal components. The first one is correlated positivelywith SiO2 and negatively with MgO, CaO and loss on ignition(LOI), which can be interpreted as a mixture of the major miner-als dolomite and quartz. The second component correlates with Zn,Cd, and Mn and can be related to the presence of smithsonite andMn oxides with incorporated or adsorbed Cd. The third componentcorrelates Al2O3, Fe2O3, Na2O, K2O, Pb and As and represents thecommon fine-grained mixture of Fe oxides and clay minerals.

4.2.1. Zn carbonates, silicates, and aluminosilicatesSmithsonite occurs as fillings of cavities in dolomite (Fig. 3a), as

separate massive or botryoidal aggregates of variable size or pseu-domorphs after sphalerite crystals (Fig. 3b). Smithsonite surface isoften etched, especially in the uppermost soil horizons. Apart fromZn, smithsonite contains trace amounts of CdO (average 0.2 wt%),PbO (0.6), FeO (0.2), CaO (0.7), and MgO (0.2). The average concen-tration of arsenic (0.08 wt%) is near the detection limit of the EMP.

Several representative EMP analyses are listed in Table 3.

Hemimorphite is common in soil horizons from the site 17, infre-quent in the dump material of this site, and rare as overgrowths ofsmithsonite at the site 24. It forms radial aggregates of elongated

e, Fe oxides, and sheet silicates. Note that smithsonite fills cavities in dolomite; (b)l of Zn-containing sheet silicates with dolomite and Mn oxides; (d) Zn-containing

398 I. Jerzykowska et al. / Chemie der Erde 74 (2014) 393–406

Table 3Representative electron microprobe analyses of sheet silicates, hemimorphite, smithsonite, dolomite, and Mn oxides. All data in wt.%. n.a. = not analyzed.

Sample SiO2 TiO2 Fe2O3 Al2O3 CaO MgO ZnO MnO BaO PbO CdO K2O As2O5 SO3 Total

Sheet silicates24A 39.15 1.90 5.86 14.75 0.56 1.32 19.89 0.02 0.00 0.28 0.02 1.39 0.00 0.00 85.1224B 42.41 0.49 5.08 17.63 0.62 1.37 17.84 0.00 0.00 0.23 0.00 1.25 0.00 0.00 86.9324B 25.90 0.46 28.56 12.17 0.56 1.04 12.99 0.02 0.00 0.88 0.00 1.58 0.30 0.16 84.6324C 32.30 0.09 4.32 21.74 0.43 0.57 16.93 0.03 0.13 0.18 0.00 0.87 0.00 0.27 77.8317A 34.33 0.01 1.69 5.98 0.33 2.12 37.03 0.09 0.12 0.00 0.01 0.25 0.00 0.06 82.0217B 37.08 0.42 5.49 10.74 0.74 1.21 26.15 0.03 0.00 0.09 0.00 0.82 0.05 0.14 82.9517B 41.02 0.13 6.33 11.16 0.70 1.50 23.05 0.00 0.02 0.09 0.01 1.66 0.00 0.06 85.7317B 36.29 0.35 4.47 10.74 0.47 0.98 23.44 0.18 0.00 0.00 0.02 0.86 0.00 0.17 77.9917C 41.00 0.08 2.53 9.83 0.83 1.50 30.67 0.04 0.08 0.00 0.00 0.99 0.00 0.21 87.7517C 37.37 0.59 5.32 13.84 0.62 1.55 6.31 0.03 0.00 0.13 0.00 1.69 0.00 0.06 67.5117C 37.80 0.31 3.62 15.76 0.52 1.99 6.50 0.00 0.00 0.09 0.00 1.49 0.00 0.11 68.21

Hemimorphite17A 27.00 0.00 0.29 0.00 0.19 0.00 72.39 0.03 0.00 0.10 0.06 0.00 0.24 0.00 100.2717B 27.79 0.01 1.10 0.40 0.05 0.00 70.02 0.00 0.16 0.31 0.00 0.08 0.02 0.02 99.8417C 28.77 0.05 0.09 0.04 0.04 0.00 69.69 0.06 0.00 0.24 0.00 0.04 0.01 0.08 99.10

Smithsonite or dolomite24A n.a. n.a. 0.05 n.a. 0.57 0.00 62.73 0.07 n.a. 1.33 0.16 n.a. 0.04 n.a. 99.76*

24A n.a. n.a. 0.23 n.a. 0.55 0.10 62.43 0.07 n.a. 0.93 0.28 n.a. 0.02 n.a. 99.36*

24C n.a. n.a. 0.46 n.a. 31.35 19.57 0.57 0.11 n.a. n.a. 0.06 n.a. n.a. n.a. 98.69*

Mn oxides24C 0.42 0.00 6.51 0.01 0.22 0.01 5.24 45.92 0.88 27.07 0.00 0.03 0.44 0.00 86.0817A 11.97 0.03 15.96 2.42 0.81 0.38 12.04 22.67 0.00 18.56 0.06 0.33 0.05 0.16 83.8517A 0.37 0.00 1.77 0.18 0.99 0.20 6.75 58.48 10.73 0.00 0.02 0.14 0.25 0.07 79.7717A 0.63 0.00 3.58 0.09 0.89 0.17 5.55 56.50 10.97 0.00 0.07 0.18 0.00 0.06 78.3417A 0.56 0.00 4.43 0.15 1.10 0.15 6.08 54.75 10.50 0.00 0.02 0.07 0.00 0.12 77.4717B 0.68 0.00 3.65 0.31 0.47 0.07 12.64 47.22 1.33 13.60 0.09 0.00 0.00 0.08 79.7717B 13.07 0.00 3.98 1.71 0.69 0.35 19.84 28.14 0.51 14.46 0.07 0.02 0.04 0.03 82.4917B 0.66 0.00 2.81 0.09 0.29 0.01 6.37 48.60 1.78 21.41 0.11 0.00 0.00 0.00 81.85

3

csqhstl

ipaiawifas2aoostpsogmi

sit

these two minerals to the analytical results. An explanation for theco-existence of such phases was provided by Paquet et al. (1986)who claim that trioctahedral Zn-smectites are unstable under

ZnO

17C 15.80 0.20 3.89 7.04 0.46 0.67 11.0

* Totals include CO2 calculated by stoichiometry.

rystals or massive aggregates. Hemimorphite crystallizes on theoil particles, on the Zn-aluminosilicates and occasionally on theuartz grains, indicating that it formed in the soils. In mineral soilorizons 17aII and 17bII, most of the hemimorphite grains arelightly etched. Apart from Zn and Si, only the average concen-ration of FeO exceeds 0.1 wt%. A few representative analyses areisted in Table 3.

Zn-rich sheet aluminosilicates were found in all soil profiles, butn larger amounts at the site 17. They form large (up to 500 �m)laty crystals (Fig. 3c) or aggregates of small particles; they maylso occur together with Fe oxides in rims around various grainsn soils (Fig. 3a and d). Characteristic is the occurrence of Zn-luminosilicates in etch pits in smithsonite and hemimorphitehich indicates that the released Zn precipitated as aluminosil-

cates. XRD analysis revealed three types of minerals in the clayraction. The first mineral is characterized by the first basal peakt d ∼ 15 A in air-dried conditions which shifts to d ∼ 17 A afteraturation with glycol and collapses to d ∼ 10 A after heating to20 ◦C. This behavior is typical for smectite-group minerals but thebsence of rational series of reflections indicates that the presencef mixed-layered clay minerals cannot be excluded (illite-smectiter kaolinite-smectite, R = 0; Srodon, 2006). The minerals of theerpentine-kaolinite group are characterized by the interlayer dis-ance of 7.12–7.18 A in air-dried conditions; the corresponding XRDeak disappears at 550 ◦C. The structure of the mineral does notwell after glycol saturation. Mica-group minerals were recognizedn the basis of the peak at 10 A which does not change position afterlycol saturation. The clay fraction is dominated by smectite-groupinerals and kaolinite-group minerals, mica-group minerals occur

n minor amount.

The results of EMP analyses of the sheet silicates are rather

cattered (Fig. 4, Table 3). The amount of Zn in most of the analysess too low for stoichiometric sauconite [Zn trioctahedral smec-ite Na0.3Zn3(Si,Al)4O10(OH)2·4H2O]. The formula normalized to

25.47 0.03 20.50 0.08 0.61 0.09 0.00 85.46

Si + Al = 4 is (K,Ca)0,18(Zn,Fe,Mg,Mn,Al)�2,85(Si,Al)4O10(OH)2·4H2O.Pure kaolinite was not observed, either by EDS- or WDS-EMPanalyses, implying that kaolinite in the clay fraction also containsZn in its structure. Some of the analyses are close to fraipontite –Zn trioctahedral mineral [(Zn,Al)3(Si,Al)2O5(OH)4] of serpentine-kaolinite group. It is likely that the analyzed material consists ofa fine-grained mixture of sauconite and fraipontite and the spatialresolution of the EMP does not allow to separate the contribution of

Fe O2 3 MnO

Fig. 4. Triangle diagram showing the composition of Fe oxides (diamonds), Mnoxides (squares), Zn-containing sheet silicates (open circles), and smithsonite, hemi-morphite (gray circles). All data are spot EMP analyses.

ie der Erde 74 (2014) 393–406 399

wwsp

ccntc

4

maafiiw

1.0 2.0 3.0 4.0R + R (Å)Δ

χ(R

) (

Å)

-4

Fig. 5. FT EXAFS data for the Zn-containing sheet silicates, collected at the Zn Kedge. Circles represent the measured and processed data, solid line is the fit. For

FRc

I. Jerzykowska et al. / Chem

eathering conditions and transform to dioctahedral smectitesith time. On pedogenic time scales (up to 10,000 years), the

mectites further change to Zn-kaolinite and Zn-goethite. Such arocess could have also operated at the site studied in this work.

The Zn K edge EXAFS spectra, collected on the clay fraction,onfirm that Zn is incorporated in the structure of the sheet sili-ates (Fig. 5). According to the refinement, each Zn atom has ∼4 Zneighbors in the second shell, meaning that the clays, be they fromhe smectite or serpentine-kaolinite group, are Zn rich or that Znlusters in their structures (Table 4).

.2.2. Fe and Mn oxidesFe oxides concentrate in the soil horizons II where they form

assive and porous aggregates of different sizes. Internally, theseggregates are often zoned (Fig. 6a) or they are pseudomorphs

fter the primary iron sulfides (Fig. 6b and c). Fe oxides may be veryne-grained (Fig. 6d) and also replace organic fragments. Accord-

ng to the �-XRD results, Fe oxides consist mainly of goethite,ith occasional admixture of hematite or rarely other minerals.

ig. 6. Scanning electron microphotographs of (a) a zoned grain of Fe oxides; (b) a pseudoelics of the primary marcasite are still present; (d) a fine-grained, porous aggregates of Fontribution in their formation; (f) masses of Mn oxides in the voids of organic material.

quantitative interpretation of the data, see Table 4 and text.

morph of Fe oxides after Fe sulfides; (c) a pseudomorph of Fe oxides after marcasite.e oxides; (e) a similar morphology of Mn oxides, suggestive perhaps of a biological

400 I. Jerzykowska et al. / Chemie de

Table 4Results of the refinement of the structural model for the Zn-clays from the EXAFSmeasurements on the Zn K edge (Fig. 5). �E0 = 1.2(2.2). Data for the fit were takenbetween k = 2.5 and k = 12.4 A−1 and (R + �R) = 1.0 to (R + �R) = 3.5 A. Number ofindependent data points 21.74, number of refined variables 8 (the variables wererefined successively, not all simultaneously). Statistics of the fit: reduced �2 = 1301.All parameters computed or refined by the software package Artemis (Ravel andNewville, 2005).

Path (s) CN R (Å) �2

Zn–O 6.2(1.7) 2.08(2) 0.009(4)Zn–Zn and Zn–Si* 4.6(1.7) Zn–O 3.09(2) 0.009(3)

Si–O 3.30(2)

Mthss(bF(hcaf

includes MnO and PbO and corresponds likely to Mn oxides. The

TR

TR

* Both paths refined with one set of parameters (CN, �r, �2).

össbauer spectroscopy revealed that Fe oxides aggregates con-ains 80–100% of high-spin Fe3+ (in nanoparticles) and up to 20%igh-spin Fe2+ (Table 5). The most probable location of the highpin Fe3+ is within goethite nanoparticles as low temperaturepectra are consistent with the corresponding goethite spectraBroz et al., 1990; Berquó et al., 2007). This hypothesis is supportedy the lack of magnetic order at room temperature. The high-spine2+ has the same hyperfine parameters as iron located in ankeriteDe Grave and Wochten, 1985; De Grave, 1986). Moreover, theigh amount of Fe2+ in the samples 17aI and 24aI (dump material)

orrelates well with the abundance of carbonates of the dolomite-nkerite series (as determined by XRD). There is 14% of Fe in theorm of Fe3O4 in the sample 17aIII, probably from dust particles.

able 5esults of the Mössbauer spectroscopy analysis of the studied samples, with the fitting p

Sample/Fe form Content (%) (±1%) S (mm/s)

17aI RTFe3+ 80 0.36(1)

Fe2+ 20 1.26(2)

17aIII RTFe3+ 82 0.35(1)

Fe2+ 4 1.61(2)

Fe3O4 14 (9 + 5) 0.36(1)

0.54(2)

24aI RTFe3+ 87 0.36(1)

Fe2+ 13 1.39(2)

24aI 80K34

Fe3+ 25 0.49(2)

25

Fe2+ 16 1.36(1)

24aII RTFe3+ nanoparticles – –

24aII 80KFe3+ nanoparticles 92 0.49(1)

�-FeOOH 8 0.44(2)

able 6epresentative electron microprobe analyses of Fe oxides. All data in wt.%.

Analysis SiO2 TiO2 Fe2O3 Al2O3 CaO MgO

14II1-F2 1.65 0.00 86.32 0.01 0.16 0.00

14II2-B5 2.46 0.00 73.66 0.01 0.16 0.14

14II2-F4 8.24 0.04 75.93 0.71 0.63 0.30

17II1-A2 4.19 0.00 52.15 0.44 0.25 0.17

17II1-D3 3.37 0.00 80.52 0.37 0.12 0.03

17II1-G1 20.28 0.09 54.45 7.57 0.35 1.31

24II1-B3 11.02 0.12 61.89 3.46 0.42 0.49

24II1-G1 7.30 0.53 69.54 5.04 0.37 0.38

24II2-A7 2.15 0.09 83.53 1.94 0.14 0.07

24II2-D2 8.19 0.03 73.32 4.71 0.17 0.51

r Erde 74 (2014) 393–406

We also identified lepidocrocite (�-FeOOH) as a minor component(7%) in the sample 24aII (Table 5). Lepidocrocite was not identifiedduring �-XRD studies but its presence in Polish non-sulfide Zndeposits was mentioned by Cabała (2001). Fe oxide aggregatescontain considerable amounts of Zn, Pb, As and Cd (Table 6), withthe mean values of 5.02 wt% Zn, 1.29 wt% Pb, 0.15 wt% As, and0.03 wt% Cd.

Mn oxides occur mainly in soils horizons II from sites 14 and 17.They form porous (Fig. 6e), often layered aggregates filling cracks indolomite, overgrowing soil grains, or replacing and filling organicfragments (Fig. 6f). Mn oxides contain high amount of PbO witha mean value of 12.87 wt% Pb. The co-occurrence of Mn oxidesand Pb has been observed in many similar weathering environ-ments (e.g., Eusden et al., 2002; Rollinson et al., 2011; Miler andGosar, 2012). Soil Mn-oxides, especially biogenic birnessite, havea high capacity for Pb accumulation (Nelson et al., 1999; O’Reilly,2002; O’Reilly and Hochella, 2003). Other minor elements in theMn oxides are (on average) 5.73 wt% Zn, 0.03 wt% As, and 0.05 wt%Cd. Grains containing smaller amounts of Pb contain often Ba.

Fe oxides often occur in mixtures with clay minerals and Mnoxides enriched in Pb. A PCA analysis of the EPMA results identifiedfour components. The first one is correlated with SiO2, MgO, Al2O3and K2O and corresponds to clay minerals. The second component

third component is Fe2O3 and represents the Fe oxides and the lastcomponent is ZnO. ZnO is probably a separate component becauseit may be associated with both sheet silicates and Fe oxides.

arameters and the assignment of the absorption bands.

� (mm/s) B (T) � (mm/s)

0.61(1) – 0.35(1)1.46(2) – 0.43(4)

0.59(1) – 0.35(1)0.91(3) – 0.43(5)−0.13(3) 50.4(1) 0.55(4)0.04(4) 45.5(2)

0.58(1) – 0.35(1)1.22(2) – 0.43(5)

46.6(1) 0.36(3)−0.22(2) 48.5(1) 0.22(2)43.5(3) 0.8(1)1.94(2) – 0.45(5)

– – –

−0.23(2) 47.5(4) 0.30(5)0.73(2) – 0.50(5)

ZnO MnO PbO K2O SO3 As2O5 Total

3.00 0.00 2.10 0.02 0.22 1.07 94.555.41 0.05 0.54 0.01 0.19 0.42 83.068.80 0.03 1.20 0.02 0.09 0.43 96.425.04 0.00 0.30 0.00 0.07 0.39 63.026.53 0.03 1.61 0.00 0.17 0.00 92.749.07 0.01 0.30 1.20 0.04 0.00 94.666.12 0.03 1.31 0.45 0.23 0.37 85.927.55 0.04 1.61 0.49 0.17 0.40 93.405.24 0.00 1.11 0.05 0.33 0.77 95.415.86 0.01 0.70 0.54 0.47 0.00 94.51

I. Jerzykowska et al. / Chemie der Erde 74 (2014) 393–406 401

exchangeable cations carbonates Mn oxides amorphous Fe oxides

crystalline Fe oxides organic matter residual fraction

ho

rizo

n

I

II

III

Pb14 17 24 25

samples

Cd14 17 24 25

samples

I

II

III

As14 17 24 25

samples

I

II

III

Zn14 17 24 25

samples

I

II

III

ho

rizo

n

y of th

4

4

mailsrcri

iceswm(sitsmca

hemimorphite in the soils. The Fe oxides bind not only As but alsoZn (see Fig. 8).

Cadmium, as mentioned above, is probably geochemically cou-pled to zinc. The largest difference in the behavior between Cd and

Fe O /102 3

Fig. 7. Graphical summar

.3. Speciation of Zn, As, Cd, and Pb in the mining waste

.3.1. Sequential extractionsResults of sequential extractions are summarized in Fig. 7. The

ost striking feature is the difference in the speciation between Asnd Zn, Cd, Pb. Arsenic is extracted mostly in the reducible fraction,ndicating its association with iron oxides, mostly crystalline, to aesser extent X-ray amorphous. The �-XRD and Mössbauer datahowed that the Fe oxides consist mostly of crystalline goethite,arely hematite, and therefore most of the arsenic should be asso-iated with goethite. The amount of As in fractions other thaneducible (i.e., oxidizable, acid-soluble) is higher in the dumps thann the soil profiles.

Zinc, cadmium and lead, on the other hand, are released mostlyn the acid-soluble fraction, to a lesser extent, in the case ofadmium, in the exchangeable fraction. This observation can bexplained well from the association of Zn with carbonates (smith-onite or dolomite). An exception are the samples from site 17here Zn is released in acid-soluble and reducible fractions but theineralogical analysis pointed at the absence of smithsonite there

cf. Table 2). Therefore, Zn stored in hemimorphite and Zn-richheet silicates is extracted in the same solutions as the carbonates;t is also possible that some Zn resides in dolomite. This extrac-ion behavior is interesting and highlights the inefficiency of the

equential extractions to distinguish different reservoirs of an ele-ent, although they may appear to be chemically distinct (i.e.,

arbonates versus silicates). The amount of Zn bound to reduciblend oxidizable fraction increases toward the top of the profiles

e sequential extractions.

while the acid-soluble fraction decreases toward the top. This trendcan be rationalized by the greater abundance of Fe oxides in thesoils than in the dumps and by the dissolution of smithsonite and

As O2 5 ZnO

Fig. 8. Triangle diagram of the bulk analysis of the studied material (diamonds, ICPdata) and the spot analyses of iron oxides (circles, EMP analyses).

402 I. Jerzykowska et al. / Chemie der Erde 74 (2014) 393–406

F rph) oo

Zbbro

otm

esroThacm

ig. 9. Distribution of major, minor, and trace elements in an aggregate (pseudomof counts).

n is the abundant release of Cd in the exchangeable fraction. Thisehavior is observed particularly in the horizons II and III and coulde related to the binding strength and capacity of Fe oxides. Theesults could be interpreted by a weaker sorption of Cd to the Fexides in comparison to Zn.

Zinc and cadmium in the samples 14 and 17 show affinity forrganic matter. This association was not further investigated ashis work targeted the inorganic constituents of the system, i.e.,

inerals.The speciation of lead is somewhat more difficult to explain. The

xtraction in the acid-soluble fraction (30–95% of total Pb) coulduggest that lead occurs in the form of carbonates but our EMPesults indicate that lead appears to be associated mostly with Mnxides and part of it may be released in the acidic buffer solution.he enhanced extraction of Pb in the reducible fraction from the

orizon II from the sites 14 and 17 correlates well with the higherbundance of Mn oxides in these samples. In some samples (espe-ially 14 and 17), lead associates to a larger degree with organicatter.

f Fe oxides (EMP mapping, the relative concentration is shown in a scale of number

4.3.2. Electron microprobe (EMP) elemental mapping andanalyses

Mapping and analytical work with an electron microprobereveals association and correlation of elements with certain typesof matrices. Fe oxides, as mentioned above, occur either as pseu-domorphs after the primary Fe sulfides (pyrite, marcasite) or aszoned grains which probably precipitated from the supergene flu-ids. In the pseudomorphs, we observed zones with elevated contentof As and Zn (Fig. 9). Arsenic and zinc correlate well but there is nocorrelation of these two elements with either Si or Pb. These cor-relations suggest that the Fe oxides act as a sink of many, but notall elements which may be mobile in the supergene zone. Interest-ingly, both As (usually present as arsenate anions) and Zn (usuallypresent as a cation) are retained by the Fe oxides, in agreement withthe results of sequential extraction. The spatial association of Zn and

As cannot be explained by impurities in the primary sulfides. Pyriteand marcasite do often contain elevated concentrations of arsenic(e.g., Kolker and Nordstrom, 2001) but they do not contain Zn, apartfrom negligible traces. Therefore, the zones in the pseudomorphs

I. Jerzykowska et al. / Chemie der Erde 74 (2014) 393–406 403

1.00.0 2.0 3.0 4.0

14II2-B

17II1-F

17II1-H

As-HFO

scorodite

R + R (Å)Δ

FT

magnitu

de

Fw

ao

4

aos(ets

owscb

dhsFsbrwso

Table 7Results of the refinement of the structural model for the goethite with As fromthe EXAFS measurements on the As K edge (Fig. 11). �E0 = 5.6(0.5). Values in squarebrackets were kept fixed or restrained. Data for the fit were taken between k = 1.7 andk = 13.4 A−1 and (R + �R) = 1.0 to (R + �R) = 4.5 A. Number of independent data points32.85, number of refined variables 11 (the variables were refined successively, notall simultaneously). Statistics of the fit: �2 = 24.39, reduced �2 = 1.12. All parameterscomputed or refined by the software package Artemis (Ravel and Newville, 2005).

Path(s) CN R (Å) �2

As–O 4.1(2) 1.70(1) 0.003(1)As–Fe 0.4(2) 2.76(3) 0.006(2)

2

ig. 10. A comparison of the As K edge FT EXAFS spectra of the studied Fe oxidesith standards and compounds with known local structure.

s well as the zones in the newly formed grains document episodesf element mobility under the supergene conditions.

.3.3. X-ray absorption spectroscopy (XAS)The close spatial correlation between the elements As and Zn

nd goethite led us to a more detailed investigation of the speciationf these two elements. We have applied X-ray absorption near-edgetructure (XANES) and extended X-ray absorption fine-structureEXAFS) spectroscopy at the As K or Zn K edge to determine the localnvironment of these elements in goethite. The XANES spectra athe As K edge showed that As is present in the pentavalent oxidationtate.

To strengthen the interpretation of the As XAS data, the spectraf lollingite, arsenolite, scorodite, and As-rich hydrous ferric oxidesere collected together with the data of our samples. The EXAFS

pectra of the four standards were processed and agreed with therystallographic structure of the three minerals and the bidentate-inuclear arsenate complex for the As-rich hydrous ferric oxide.

The first shell of As atoms consists of 4 oxygen atoms with aistance of 1.70(1) A, both parameters typical for As5+ in tetra-edral coordination. The second shell deviates from the secondhell of ferrihydrite or hydrous ferric oxide with sorbed As5+ (cf.ig. 10) or scorodite. We tried to refine a number of models for thepectra of our samples. Statistically, the best models, as indicatedy the goodness-of-fit variable returned by the Artemis software,

equired the presence of multiple-scattering paths where the CNas fixed to 12. The CN of 12 is the theoretical number of multiple-

cattering paths derived from the consideration of the geometryf the arsenate anion. Additionally, the prominent feature at 2.3 A

As–O–O–As [12] 3.16(4) [2� As–O]As–Fe 0.9(3) 3.31(2) [�2

As–Fe]

(uncorrected for phase shift) had to be taken into account. Incor-poration of a bidentate-mononuclear complex into the modelimproved the fit and describes this feature satisfactorily (Fig. 11).The refined parameters are listed in Table 7 and warrant somediscussion. The bidentate-mononuclear complex corresponds toan edge-sharing configuration between an octahedron and atetrahedron, a rather unusual one in solid state. Tetrahedra, espe-cially the smaller ones, are thought to be reluctant to allowsuch type of a complex because of a strong electrostatic repul-sion of the two neighboring cations. Such type of a complex,however, has been proposed or observed, for example betweenselenate and the surface of goethite (Manceau and Charlet, 1994)or between arsenate and chromate and the surface of goethite(Fendorf et al., 1997; Farquhar et al., 2002). Edge-sharing Fe3+

octahedra and phosphate tetrahedra are known from the crystalstructures of sarcopside, (Fe2+,Mn,Mg)3(PO4)2 (Moore, 1972) andheterosite, FePO4 (Eventoff et al., 1972). Edge-sharing betweenoctahedra and related polyhedra and arsenate tetrahedra wasalso observed in arsenoclasite, Mn5(OH)4(AsO4)2 (Moore andMolin-Case, 1971), lammerite, Cu3(AsO4)2 (Hawthorne, 1986), andparwelite, Mn5SbO4(SiO4)(AsO4) (Moore and Araki, 1977). Withthe exception of heterosite, in all these cases is the central octahe-dral cation divalent. Such configuration appears to be more likelythan edge-sharing between arsenate and an octahedron of a triva-lent cation. For our samples, an alternative explanation would beedge sharing between arsenate tetrahedra and the octahedra ofthe abundant Zn2+. The two possibilities (octahedra occupied byZn2+ or Fe3+) are difficult to distinguish because of the similar scat-tering power of Zn and Fe. The other As–Fe distance seen in theEXAFS spectra can be interpreted as a bidentate-binuclear complexcommonly found for arsenate adsorbed onto iron oxides.

The existence of the bidentate-mononuclear complexes, eitherwith Zn2+ or Fe3+, opens the possibility of speculation that thearsenate groups are incorporated in the structure of goethite anddo not only reside on the surface of the particles. The mecha-nism of incorporation is unknown. What could be said is that anoxidation zone, with its long geological time of ripening, wouldbe an ideal site for the occlusion and incorporation of foreigncations into the structures of supergene products. Recently, wehave observed a significant amount of As5+ and Sb5+ in the structureof goethite (Majzlan et al., 2011) where an inspection of the sam-ples in high-resolution transmission electron images did not revealany additional phase. These samples came from a tailing pond withmuch shorter history (less than 100 years) and document the abil-ity of goethite to pick up and to store many elements, even if theircoordination polyhedra may not readily fit into its structure.

The first shell in the Zn K edge spectra was satisfactorily fitwith a mixture of tetrahedrally and octahedrally coordinatedZn. Because of the presence of both coordination polyhedra, we

did not perform shell-by-shell fitting of the Zn EXAFS spectra. Anumber of paths could be expected with a severe overlap of theEXAFS oscillations. Positions of the features in the second shell

404 I. Jerzykowska et al. / Chemie der Erde 74 (2014) 393–406

2.0 4.0 6.0 8.0 10.0 12.0 1.00.0 2.0 3.0

k (Å )–1

χ()·

(Å

)kk3

3–

R + R (Å)Δ FT

ma

gn

itud

e o

r re

al p

art

Fig. 11. EXAFS (left) and FT EXAFS (right, magnitude and real part) of the XAS data for Fe oxides, collected at the As K edge. Circles represent the measured and processeddata, solid line is the fit. For quantitative interpretation of the data, see Table 7 and text.

2 3 4 5 6 7 8 9 10 11 12 13

adamite

franklinite

goslarite

hemimorphite

hydrozincite

sphalerite

Zn hydrotalcite

Zn-smectite

zincite

Zn-goethite

goethite from the mining waste in Olkusz

1.00.0 2.0 3.0 4.0

14II2-B

17II1-A

17II1-F

Zn-goethite

R + R (Å)Δk (Å )-1

FT

ma

gn

itud

e

a b

χ()·kk3

F ll spec( ll me

co(dsfTb∼n

5

tiac

ig. 12. (a) Zn K edge k3-weighted � spectra of reference minerals and the samples (aFT) EXAFS spectra for the measured samples and the Zn-goethite for comparison. A

an be qualitatively compared to the EXAFS spectra of a numberf reference compounds (Fig. 12a). Some reference compoundszincite, franklinite, sphalerite) which deviate too much from theata from our samples were not considered at all. The samplepectra are similar to the spectrum of goethite prepared fromerrihydrite coprecipitated in the presence of Zn2+ in the solution.he two features are located at very similar positions (cf. Fig. 12b)ut their intensity does not match. In our samples, the feature at2.6 A has a greater magnitude than the feature at ∼3.0 A (bothot corrected for phase shift), unlike in the goethite sample.

. Concluding remarks

The results of weathering, mineral and geochemical transforma-

ion of the studied material near Olkusz provide a fascinating andntriguing case study for a simple reason: We have studied a paleo-cid rock drainage system which exhausted its acid-generatingapacity and has come almost to the conclusion of the primary step

tra for the sample spots measured were merged); (b) Zn K edge Fourier-transformedasured sample spots were identified as goethite by X-ray microdiffraction.

of transformations. It is clear that weathering and decomposition ofthe large amounts of pyrite and marcasite had to produce a signifi-cant amount of acid, albeit it probably could have been neutralizedby the abundant carbonate host rocks. Hence, we have an opportu-nity to investigate the future state of mine drainage systems withsimilar mineralogy and geochemistry, for example tailing pondsand dumps from hydrothermal veins with abundant carbonates.

Indeed, the studied material reached the mature stages ofthe drainage systems characterized by abundant crystalline ironoxides, mostly goethite (cf. Jambor, 2003). Zinc, the second mostabundant metal, was stored in separate secondary phases (smith-sonite, hemimorphite) but also in large amount in goethite. Aninteresting aspect shown by this study is the remobilization of zincunder the surface conditions. The evidence for these processes is

etching of smithsonite and hemimorphite and neo-crystallizationof the zinc-containing sheet silicates. Arsenic is stored relativelystrongly in goethite, as indicated by the sequential extractions. Theanalysis of the local environment of arsenic in goethite suggests

ie der

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mr(tbteTtsia(aewae

A

samogPFWc

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A

A

B

B

B

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C

C

I. Jerzykowska et al. / Chem

he existence of bidentate mononuclear complex, in addition tohe more common bidentate binuclear complex. We interprethese findings as incorporation of arsenic into the crystal structuref goethite, something worth further studies. Recently, we havehown that the tetrahedrally coordinated As5+ can be efficientlyncorporated into the structure of hematite (Bolanz et al., 2013)nd perhaps a similar mechanism can be found for goethite.

Overall, this study shows that the mature system binds theetals from the primary sulfides relatively strongly. Yet, some

elease of the metals is observed in laboratory (Fig. 7) and in naturee.g., Zn phyllosilicates). This aspect is also of interest – the condi-ions in the oxidation zone and on the surface are largely similarut the metals, to a certain extent, are mobile. We may speculatehat their mobility near the surface, in the mining waste, may benhanced by a higher water/rock ratio than in the oxidation zone.his result can imply that although the studied material is rela-ively benign, especially when compared to active mine drainageystems with high loads of toxic elements (e.g., Majzlan et al., 2011),t still has a potential to cause local environmental problems. Theyre known from the broad area of the Polish MVT-type depositse.g., Czop et al., 2007) and include contamination by heavy metalsnd sulfate. The work by Czop et al. (2007) and by others, how-ver, describe the water quality in the discharge from the miningorks, not water quality affected by leaching of the mining waste

nd mining residuum. The two cases must be strictly distinguished,ven though they may appear geochemically very similar.

cknowledgements

We thank the Karlsruhe Institute of Technology for the provi-ion of the beam time at the Angströmquelle Karlsruhe (ANKA). J.M.ppreciates the financial support from the Deutsche Forschungsge-einschaft (DFG) Research Training Group GRK 1257/1. The work

f I.J. was supported by Doctus - Malopolska scholarship fund forraduate students (2008), within the Human Capital Operationalrogramme for 2007–2013 (POKL), financed from European Socialund, the state budget and the budget of the Malopolska Region.e are thankful to two anonymous reviewers for their constructive

riticism.

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